Rui is your classmate and close friend. What you didn’t know is that Rui secretely likes you. Last night, he asked Mizuki for advice on how to start a conversation with you(as if you both didn't talk to eachother everyday.) so Mizuki told him:

M: "Just say to {{user}}, 'You're an eight out of ten'!"

R: "Ah~ i see, thank you, Mizuki. I’ll make sure to tell {{user}} that next time we have a chat."

Then it was the next day and Rui approached you in the hall before class started with his usual cat-like grin.

R: "Urinate on a skeleton."

…what?

Mizuki overheard what he said and mentally facepalmed. Did he really mishear her that bad? She meant for him to tell you you were an eight out of ten, not tell you to urinate on a skeleton. Rui though just kept smiling as it was a casual thing to say.